Storage

ABSTRACT

A method and apparatus for delivering content to a user are disclosed. A data bit-stream is provided having a base layer data bit-stream and at least one enhancement layer data bit-stream. The data bit-streams are stored separately in a storage device. The stored content is then offered at different quality levels. When a request is received from the user for the content at a specified quality level, the base layer data bit-stream and however many enhancement layer data bit-streams that are needed to produce the specified quality level are downloaded to the user.

FIELD OF THE INVENTION

The invention relates to the storage of video content, and moreparticularly to a method for selling the same stored video content atdifferent quality levels.

BACKGROUND OF THE INVENTION

Many video applications are enabled where video is available at variousresolutions and/or qualities in one bit-stream. Methods to accomplishthis are loosely referred to as scalability techniques. There are threeaxes on which one can deploy scalability. The first is scalability onthe time axis, often referred to as temporal scalability. Secondly,there is scalability on the quality axis (quantization), often referredto as signal-to-noise (SNR) scalability or fine-grain scalability. Thethird axis is the resolution axis (number of pixels in image) oftenreferred to as spatial scalability. In layered coding, the bit-stream isdivided into two or more bit-streams, or layers. Each layer can becombined to form a single high quality signal. For example, the baselayer may provide a lower quality video signal, while the enhancementlayer provides additional information that can enhance the base layerimage. With spatial scalability, the base layer video may have a lowerresolution than the input video sequence, in which case the enhancementlayer carries information which can restore the resolution of the baselayer to the input sequence level.

Typically, these scaled video bit-streams are stored together in astorage device by the content provider or service provider, so thequality level of the stored video content is fixed by the processingwhich was performed prior to storing the content. A user can access thestorage device or the storage device can download the scaled videobit-streams for display at a user device.

SUMMARY OF THE INVENTION

If a service or content provider wants to offer the video content forsale at different quality levels, the same video content will need to beprocessed and stored for each quality level offered for sale. This canbe very problematic from a storage stand point since video data consumeslarge quantities of storage space. Thus, there is a need for a methodand apparatus for providing a way to offer for sale the same storedvideo content at different quality levels without having to store thecontent multiple times. The invention overcomes the deficienciesdescribed above by storing the different layers of video bit-streamsseparately in an elastic storage device, wherein the elastic storagedevice sends the appropriate video bit-streams to the user to create afinal video bit-stream with a selected quality level.

According to one embodiment of the invention, a method and apparatus fordelivering content to a user are disclosed. A data bit-stream isprovided having a base layer data bit-stream and at least oneenhancement layer data bit-stream. The data bit-streams are storedseparately in a storage device. The stored content is then offered atdifferent quality levels. When a request is received from the user forthe content at a specified quality level, the base layer data bit-streamand however many enhancement layer data bit-streams that are needed toproduce the specified quality level are downloaded to the user.

According to another embodiment of the invention, a method and receiverfor receiving multilayered content which can be displayed at differentquality levels are disclosed. Layered content is received comprising abase layer bit-stream and at least one enhancement bit-stream. Aselected quality level of display is received for the layered content. Adetermination as to which enhancement-bit-streams need to be combinedwith the base layer bit-stream to create the selected quality level isthen made. The combination of selected streams are then displayed.

These and other aspects of the invention will be apparent from andelucidated with reference to the embodiments described hereafter.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example, with referenceto the accompanying drawings, wherein:

FIG. 1 is a block diagram of a video content distribution systemaccording to one embodiment of the invention;

FIG. 2 is a block diagram of an elastic storage device according to oneembodiment of the invention;

FIG. 3 is a block diagram of a layered video encoder according to oneembodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

According to one embodiment of the invention, scalable video content isstored in an elastic memory device. While the following illustrativeexamples will discuss stored video data, it will be understood by thoseskilled in the art that the invention also applies to other stored data,e.g., audio data, audio/video data, but the invention is not limitedthereto. For storing data items such as digital video, audio and imageson a storage medium with a fixed capacity, elastic storage is a veryefficient way of utilizing the storage capacity of the medium. Theprinciples of elastic storage are described in the published EuropeanPatent Application No. WO0169939 of the applicant, entitled “CompressedStorage Of Data Items”. According to the elastic storage principle, adigital data item to be stored is first divided into successive datapieces of decreasing significance. Consequently, the data pieces arestored in a memory provided there is enough space to accommodate all thepieces. In case the memory does not have enough space, space is createdby removing from the memory those data pieces from various items thathave the lowest significance. The thus freed space is used for storingthe data pieces of the data item to be stored. Preferably, an auxiliarymemory is used for recording the identification data, such as file nameand significance, of all the data pieces stored in the memory.

As illustrated in FIG. 1, a service provider or content provider encodesthe video content in an encoder 102 using a known scalable compressionmethod. The encoded video content is then sent to the storage device104, for example, a set-top box. In this embodiment, the encoder 102 canbe a transmitter and the storage device 104 can be a receiver, whereinthe signals form the encoder 102 to the storage device can betransmitted through various medium such as, for example, air, cable,fiber optic cables, etc. The storage device 104 stores each layer of theencoded video bit-stream, for example, a base layer 202, a firstenhancement layer 204 and a second enhancement layer 206, separately asillustrated in FIG. 2. In this embodiment, the base layer videobit-stream and the two enhancement layer video bit-streams are storedseparately in the storage device 104. When a user device 106 requeststhe video content to be delivered with a specified quality level, astorage controller 208 selects the different layers of video bit-streamswhich are needed to reproduce the video content with the specifiedquality level. It will be understood by those skilled in the art thatthe storage device 104 and the user device 106 can be incorporated intoa single device such as, for example, a television, computer, etc. Asmentioned above, the invention is not limited to video data but alsoextends to other stored data such as audio data. For example, the baselayer could be used for mono or stereo sound while the enhancement layercan be used to extend the sound to, for example, full 5.1 surroundsound.

The business model of selling the same content at different qualitylevels is closely related to elastic storage, since there too the samecontent is stored at multiple quality levels using scalable compression.The quality levels that are offered for purchase to the consumer cancorrespond to the quality levels used in the elastic storage system.This implies that when the elastic storage device wants to lower thequality of a certain content item, the device can remove the highestencrypted layer, without needing to decrypt the layer. Since the devicedoes not decrypt any data, there is no security or theft risk. Tomaintain security in the whole chain from the content owner or serviceprovider to the consumer, the content is preferably compressed, e.g.,using a scalable compression method, and encrypted at the desiredquality levels by the content owner and then distributed in encryptedform to the elastic storage device either directly transmitted ordownloaded or indirectly via e.g., intermediate storage on an opticaldisk.

FIG. 3 illustrates a known spatial scalable video encoder 300. Whilethis illustrative example just has a base layer and one enhancementlayer, it will be understood by those skilled in the art that theencoder can have any number of enhancement layers and the invention isnot limited thereto. The depicted encoding system 300 accomplishes layercompression, whereby a portion of the channel is used for providing alow resolution base layer and the remaining portion is used fortransmitting edge enhancement information, whereby the two bit-streamsmay be recombined to bring the system up to high-resolution. The highresolution video input is split by splitter 302 whereby the data is sentto a low pass filter 304 and a subtraction circuit 306. The low passfilter 304 reduces the resolution of the video data, which is then fedto a base encoder 308. In general, low pass filters and encoders arewell known in the art and are not described in detail herein forpurposes of simplicity. The encoder 308 produces a lower resolution basebit-stream which can be broadcast, received and via a decoder, displayedas is, although the base bit-stream does not provide a resolution whichwould be considered as high-definition.

Via a splitter 310, the output of the encoder 308 is also fed to adecoder 312 within the system 300. From there, the decoded signal is fedinto an interpolate and upsample circuit 314. In general, theinterpolate and upsample circuit 314 reconstructs the filtered outresolution from the decoded video bit-stream and provides a video databit-stream having the same resolution as the high-resolution input.However, because of the filtering and the losses resulting from theencoding and decoding, loss of information is present in thereconstructed bit-stream. The loss is determined in the subtractioncircuit 306 by subtracting the reconstructed high-resolution bit-streamfrom the original, unmodified high-resolution bit-stream. The output ofthe subtraction circuit 306 is fed to an enhancement encoder 316 whichoutputs a reasonable quality enhancement bit-stream. Optionally, theencoder 300 may also include encryption devices 318 and 320 to encryptthe base layer video bit-stream and the enhancement layer videobit-stream, respectively. Preferably, each encoded video bit-stream isencrypted with a different encryption. It will be understood by thoseskilled in the art that a single encryption device could also be used toencrypt each encoded video bit-stream.

In an elastic storage application using this embodiment of theinvention, the user (or the device based on what it knows about thepreferences of the user) may optionally select a certain desired minimumquality level, i.e., content that is currently available at a higherquality level than minimally desired by the user may be reduces inquality to make room for more different content, until it reaches thelowest quality level acceptable to the user. When the content is stillavailable in a higher quality, however, the user still has the option topurchase the higher quality. Of course, the user (or device) may alsopreset different desired minimum quality levels for different types ofcontent (like sports, talk shows, or movies).

Alternately, it is also possible to let the service provider manage thestorage space and determine which quality levels should be removed (inthat case, the service provider keeps track of the qualities and maycarry out the elastic storage functions). This could be useful, e.g.,when the content is put on a set-top box containing a storage function,e.g., hard disk, by the service provider. Initially, the content couldbe offered to the user at a high quality. When the user does notwatch/buy the content within a predetermined period of time, the qualitylevel stored on the set-top box can be lowered to make room fordifferent content.

According to another embodiment of the invention, quality informationabout each layered encoded video bit-stream can be included as sideinformation which is stored with each video bit-stream in the elasticstorage device 104. Quality information and the generation of qualityinformation is described in published European Patent Application No.WO0232147. Briefly, the quality information is generated by the encoder300 in a quality information generator 322. The quality informationgenerator 322 extracts object quality from the input video signal aswell as the signals and/or parameters provided by the encoder 300. Thequality information can indicate a quality of the object in relation tothe given position in (or a given part of) the bit-stream. By addingquality information to the bit-stream, jointly storing or transmittingmultiple coded objects can be optimized in that the quality of theobject can be easily taken into account. The quality information fromthe quality information generator 322 is provided to the encoder 300,which generates the quality information tags and inserts them into thebit-stream. The quality information is not part of each video bit-streamor alternatively can be added to the video bit-stream after theencryption process so the quality information is not encrypted asillustrated in FIG. 3. In this embodiment, the storage controller 208can read the quality information and then select which layered videobit-streams are needed to create the video content at the quality levelselected by the user.

It will be understood that the different embodiments of the inventionare not limited to the exact order of the above-described steps as thetiming of some steps can be interchanged without affecting the overalloperation of the invention. Furthermore, the term “comprising” does notexclude other elements or steps, the terms “a” and “an” do not exclude aplurality and a single processor or other unit may fulfill the functionsof several of the units or circuits recited in the claims.

1. A method for delivering content to a user, comprising the steps of:providing a data bit-stream having a base layer data bit-stream and atleast one enhancement layer data bit-stream; storing the base layer databit-stream and the at least one enhancement layer data bit-streamseparately in a storage device; offering the stored content at differentquality levels; receiving a request from the user for the content at aspecified quality level; downloading to the user the base layer databit-stream and however many enhancement layer data bit-streams areneeded to produce the specified quality level.
 2. The method accordingto claim 1, wherein the data bit-stream is a video bit-stream.
 3. Themethod according to claim 2, further comprising the steps of: encryptingthe base layer video bit-stream using a first encryption; encryptingeach enhancement layer video bit-stream using different encryption. 4.The method according to claim 2, further comprising the step of: addingquality information to each video bit-stream specifying the qualitylevel of the individual video bit-stream, wherein the storage devicereads the quality information so as to download the video content withthe quality level specified by the user.
 5. The method according toclaim 2, further comprising the step of: lowering the available qualitylevel in the storage device by deleting at least one enhancement layerfor the video content when the user does not select the video contentwithin a predetermined period of time.
 6. The method according to claim2, wherein the storage device determines the specified quality levelbased on the number of different quality layers available for theselected video content.
 7. The method according to claim 1, wherein thebase layer data bit-stream and the at least one enhancement layer databit-stream are encoded prior to being stored.
 8. An apparatus fordelivering content to a user, comprising: means for providing a databit-stream having a base layer data bit-stream and at least oneenhancement layer data bit-stream; storage device for storing the baselayer data bit-stream and the at least one enhancement layer databit-stream separately; means for offering the stored content atdifferent quality levels; means for receiving a request from the userfor the content at a specified quality level; means for downloading tothe user the base layer data bit-stream and however many enhancementlayer data bit-streams are needed to produce the specified qualitylevel.
 9. The apparatus according to claim 8, wherein the databit-stream is a video bit-stream.
 10. The apparatus according to claim9, further comprising: first encryption means for encrypting the baselayer video bit-stream; encryption means for encrypting each enhancementlayer video bit-stream using different encryption.
 11. The apparatusaccording to claim 9, further comprising: a quality informationgenerator for adding quality information to each video bit-streamspecifying the quality level of the individual video bit-stream, whereinthe storage device reads the quality information so as to download thevideo content with the quality level specified by the user.
 12. Theapparatus according to claim 9, further comprising: means for loweringthe available quality level in the storage device by deleting at leastone enhancement layer for the video content when the user does notselect the video content within a predetermined period of time.
 13. Theapparatus according to claim 9, wherein the storage device determinesthe specified quality level based on the number of different qualitylayers available for the selected video content.
 14. The apparatusaccording to claim 8, wherein the base layer data bit-stream and the atleast one enhancement layer data bit-stream are encoded prior to beingstored.
 15. A method for receiving multilayered content which can bedisplayed at different quality levels, comprising the steps of:receiving layered content comprising a base layer bit-stream and atleast one enhancement bit-stream; receiving a selected quality level ofdisplay for said layered content; determining which enhancementbit-streams need to be combined with the base layer bit-stream to createthe selected quality level; displaying combination of selected streamson a display.
 16. A receiver for receiving multilayered content whichcan be displayed at different quality levels, comprising: means forreceiving layered content comprising a base layer bit-stream and atleast one enhancement bit-stream; means for receiving a selected qualitylevel of display for said layered content; means for determining whichenhancement bit-streams need to be combined with the base layerbit-stream to create the selected quality level; means for displayingcombination of selected streams on a display.
 17. A storage medium forstoring multilayered content which can be displayed at different qualitylevels, comprising: means for receiving layered content comprising abase layer bit-stream and at least one enhancement bit-stream; means forstoring the base layer bit-stream and the at least one enhancement layerbit-stream separately means for receiving a selected quality level ofdisplay for said layered content; means for determining whichenhancement bit-streams need to be combined with the base layerbit-stream to create the selected quality level means for downloading acombination of selected streams for display.